Papers by Keyword: Coolant

Abstract: This article studies dry hobbing of external cylindrical wheels by worm wheel hobs and reasons why some gear manufactures use hobbing without cutting fluids. Cutting fluids reduce frictional wear, provides temperature cooling of the tool or workpiece and helps flush away the chips from the cutting zone. But uneven cooling and different cutting conditions on the engaging and disengaging sides of a gear mesh provoke intensive wear of the teeth of the worm wheel hob, thus decreasing the life of worm hobs and increasing both the consumption of cutting tools and expenses for them. In this context, it becomes rather difficult to achieve efficiency and stability for the hobbing process. In the recent times, the cost of coolant disposal has been raised; in some cases, it accounts for 15-20% in terms of shop costs. Research was carried out under the following experimental conditions: a hobbing machine equipped with an automation system of high efficiency and with basic units of high static and dynamic stiffness; a high-accuracy worm hob from powdered metal wear-resistant high-speed steel of grade Р6М5К5; a workholding device with an elastic bush, and various cutting modes. Recommendations are given on using the multi-cycle hob-shifting strategy rather than the strategy of single-cycle shifting; and advantages gained by this technique are observed. Best cutting conditions and precision attained by dry gear-hobbing are described.

Abstract: Metal cutting processes such as machining or abrasive processes are related to the production of relatively large amounts of heat, as a result of the intense contact of workpiece and cutting tool. For that reason, it is often necessary to employ a cooling fluid in order to alleviate the intense and usually undesired heat-induced effects on the workpiece. Due to the cost and environmental concerns regarding cutting fluids, the heat absorbing efficiency and quantity of cutting fluids employed is always a concern. In the present work, the effect of cutting fluid type in the temperature profile of the workpiece during grinding is investigated and useful conclusions are drawn, concerning the efficiency of nanofluids as cutting fluids.

Abstract: Because of effective machining operations with a very small amount of cutting fluids, near-dry machining attracts increasing attentions for environmental and economical benefits. MQL machining has so far been recognized as the most representative near-dry method and it is highly successful in machining of most ordinary steels. Recent concern for environmentally friendly manufacturing further encourages the attempts at applying near-dry operations to machining of difficult-to-cut materials. Since titanium alloys are typical difficult-to-cut materials, this paper investigates the cutting performance of various near-dry methods in turning of a titanium alloy from the view point of elongating the tool life. Those near-dry operations include supply methods of regular MQL mist, coolant mist and hybrid mists, where the coolant mist is atomized water-soluble cutting fluid and hybrid mists are the mixture of MQL and coolant mists. The regular MQL operation provided longer tool life than that of dry machining. In addition, compared with MQL machining, the hybrid mist operations could further extend tool life and, in particular, the single coolant mist operations demonstrated the possibility of making the tool life longer than that of ordinary wet machining with flood cutting fluid supply.

Abstract: In this study, tool edge temperature was measured by a two-color pyrometer with an optional fiber. During one revolution of spindle, the tool edge passes over the fine hole at workpiece after cutting workpiece. An optical fiber inserted into the fine hole transmits infrared ray radiated from tool edge to two detectors with different spectral sensitivities. One peak signal from each detector can be obtained by each spindle revolution. The tool edge temperature can be calculated by taking the ratio of outputs from these two detectors. The relation between cutting heat calculated from cutting force and tool edge temperature was discussed. The tool edge temperature at the same cutting heat could be compared. The wet cutting condition caused lower tool edge temperature than the others at the same cutting heat. MQL and dry showed almost same tool edge temperature. The dispersion of tool edge temperature in wet cutting is wider than that in dry cutting and MQL cutting.

Abstract: The paper presents the experimental results that allow determining optimum quenching conditions for solid rocket motors (SRM) at the stage of firing bench tests (FBT) in gas dynamic tunnels (GDT) with altitude simulation. The work describes main design approaches for quenching unit enabling reduced thermal insulation (TI) destruction by 15-20% after finish of SRM operation due to aftereffect decrease, as well as reduced values of scattering of TI undamaged layer thickness up to 10% owing to uniform cooling.If necessary, drying accompanied with emissions of TI gaseous products and remnants of k-phase fuel components is run in GDT, which allows improving environmental safety of working facilities and shortening the time for evaluation of SRM design parameters.

Abstract: The authors have been conducting a research to apply strong alkali ion water (pH12 or so) to a working fluid for material removal processing. This is to cope with various problems relating to the existing water-soluble working fluid such as coolant putridity and the associated deterioration of factory environments and increased disposal costs of working fluids as well as to improve machining efficiency and tool life. In this study, the strong alkali ion water was applied to the tapping (M10) of stainless steel (SUS440C). As a result, use of the strong alkali ion water was found to contribute to the tool life improvement.

Abstract: Productivity of internal grinding processes is limited by wheel-workpiece contact area and high temperature generated during grinding. Existing internal grinding methods do not guarantee presence of coolant liquid in the heat generation zone. Usually coolant liquid from external nozzles could not penetrate turbulent air flow around grinding wheel. Assembled wheel with radially mobile segments allows increasing contact area but needs to be supported by more efficient heat evacuation system. New grinding wheel and method of internal grinding are developed and evaluated. New tool generates high speed hydrodynamic circular flow and dynamic wedges of coolant liquid in the cutting zones.

Abstract: A study on synthesis and characterization of Al₂O₃ nanoparticles for water-Al₂O₃ nanofluids as an alternative nuclear coolant has been done. The Al₂O₃ nanoparticles were synthesized from AlCl₃ using sol gel method utilizing sugar as chelating agent. The Al₂O₃ nanoparticles were mixed with water to produce nanofluids. XRD data showed that the Al₂O₃ nanoparticles crystallize in gamma alumina with crystallite size of 5.5 nm (Debye Scherrer method). Surface area of the Al₂O₃ nanoparticles was 90 m²/gram. Data of TEM showed that the particle size was smaller than 10 nm and the nanoparticle formed agglomerate with size of 60-100 nm. According to zeta potential data, the nanofluids were stable at pH 2.6-7.5 with zeta potential of 28-51 mV. The height of the nanofluid surface decreased about 20 % after 6 days. The thermal conductivity of the water-Al₂O₃ nanofluids produced in this study increased about 2.4-9.7 % compared to that of water.

Abstract: This research characterizes flow of micromist for machining purpose. Liquid lubricant with contact angle less than 5° is chosen for best wetting on workpiece and tool materials. A high nozzle air speed of 100 m/s produces micromist with 20° spherical cone angle containing droplets of 4 μm average diameter, but smaller droplets might raise an environmental concern. Preliminary comparative tests show a significant reduction of tool wear when machining 4140 steel in minimum quantity lubrication.

Abstract: An organic acid antifreeze coolant was developed in this paper which consisted mainly of deionized water, organic acid, pyrrole compound, alkali and dye. Glycol, nitrite, chromate, inorganic phosphate and other harmful additives were not contained in this formulation. The coolant overcomes the disadvantages in environmental protection, heat transfer and cost of the current technology which uses the ethylene glycol as antifreeze. The coolant has good low temperature protection, thermal conductivity and corrosion protection performance. Further more, the coolant has the advantages of simple preparation, good storage stability and a promising prospects.